Method and apparatus for operating gaseous discharge display memory panels in saturation mode

ABSTRACT

There is disclosed an improved method for controllably operating gaseous discharge display/memory panels. The operating control pulses include discharge initiating and/or discharge terminating pulses, each selected pulse being of a magnitude such that every discharge associated with each selected pulse occurs in the saturation mode and the effects of panel non-uniformity are minimized.

United States Patent [191 Petty METHOD AND APPARATUS FOR OPERATING GASEOUS DISCHARGE DISPLAY/MEMORY PANELS IN SATURATION MODE William D. Petty, Perrysburg, Ohio Assignee: Owens-Illinois, lnc., Toledo, Ohio Filed: May 8, 1972 Appl. No.: 251,007

Inventor:

U.S. Cl 1s/ ;qg y, 1 5 rag rm. Cl. 1105b 39/00 Field of Search 315/169, 169 TV References Cited UNITED STATES PATENTS 88 4/1972 Slottow et al. 315/169 TV [11] 3,821,597 June 28, 1974 Primary Examiner-Nathan Kaufiman Attorney, Agent, or Firm-E. J. Holler; Donald Keith Wedding v [5 7] ABSTRACT There is disclosed an improved method for controllably operating gaseous discharge display/memory panels. The operating control pulses include discharge initiating and/or discharge terminating pulses, each selected pulse being of a magnitude such that every discharge associated with each selected pulse occurs in the saturation mode and the effects of panel nonunifomiity are minimized.

4 Claims, 5 Drawing Figures MUL T/PLEX MULTIPLEX ADDRESS/N6 ADDRESSING CIRCUITS CIRCUITS DATA 3 CONTROL SHEEI 2 (IF 2 FIG. 4

FIG. 5

METHOD AND APPARATUS FOR OPERATING GASEOUS DISCHARGE DISPLAY/MEMORY PANELS IN SATURATION MODE BACKGROUND OF THE INVENTION Gaseous discharge display/memory panels and devices of the type to which the present invention pertain are disclosed in U.S. Letters Pat. No. 3,499,167 issued to Baker, et al. and US. Letters Pat. No. 3,559,190 issued to Bitzer, et al. Panels, as disclosed in these patents have inherent memory constituted by the storage of charges produced by discharge on one or more dielectric surfaces in contact with the gas and dielectrically or insulatively isolating the electrodes for supplying operating. potential from the gaseous medium. Typically, the electrodes are non-conductively coupled to the gas and in the case of Baker, et al. patent the dielectric is a thin glass coating on each conductor array. The conductors are arrayed in columns and rows to form a cross-conductor matrix between which a gas medium, typically a mixture of two gases, is placed at a selected pressure. For example, a neon-argon gas mixture (99.9 percent neon and 0.1 percent argon at a pressure slightly less than atmospheric) is suitable. The dielectric coatings in such panels may have a dielectric 'or insulating overcoating as disclosed in US Letters Pat. No. 3,634,719, issued to Ernsthausen. Evidence to date indicates that in normal operation of panels as described above, such panel sustains in a saturation mode, that is, the applied sustaining signal is essentially neutralized by the wall voltage formed on discharge. However, the selected addressing (both write and erase) pulse has been accomplished by attempting to set the wall voltage level at some more or less precise value by firing the cell sites in the panel at an intermediate point on the curve or plot of the change in wall voltage versus the V characteristic of the panel. Due to the stable nature of discharge sequences once initiated, deviations from this are permissible. In fact, deviations are inevitable due to panel non-uniformities so thatthe average write voltage actually produces a variety of wall voltages, V depending upon the particular site in the panel which has been selected.

In accordance with the present invention, cell sites are operated in the saturation mode so that panel nonuniformities are minimized or become irrelevant and have no significant effect on panel behavior by the application of at least one member selected from a discharge initiating (write) pulse or discharge terminating (erase) pulse. The selected pulse voltage must be at least as great as the saturation voltage for all discharges. Thus for purposes of writing and entering information to the panel, a relatively larger firing voltage pulse is used so as to achieve saturation mode in the first firing.

The above and other objects and advantages and features of the invention will become more apparent from the following specification, when considered with the accompanying drawings wherein:

FIG. 1 is a graph illustrating a prior art mode of sustaining of gaseous discharge panels,

FIG. 2 is a graph illustrating an ideal mode of ad dressing a gaseous discharge display/memory panel according to the prior art,

FIG. 3 illustrates the firing, sustaining and wall voltage waveform generators for the ideal operation illustrated in FIG. 2,

FIG. 4 illustrates the sustaining and write waveforms and the wall voltage waveform according to the ideal operation as described in the prior art,

FIG. 5 is a graph illustrating the prior art mode of panel operation as depicted in FIG. 2 and the saturation voltage as incorporated in the present invention.

In FIG. 3, gaseous discharge display panel 10, for example, of the type disclosed in Baker, et al. US. Pat. No. 3,499,167, provided with thin. overcoating on the dielectric (not shown) with the discharge gap (distance between dielectric surfaces bounding the gas) set at between 4 and 6 mils. The panel 10 is constituted by a row conductor plate 11 and a column conductor plate 12 joined in spaced apart relation by a spacer sealant 13 to provide the aforementioned discharge gap dis tance and the thin gas chamber in which the gaseous medium is placed under a suitable pressure, e.g., slightly under atmospheric and in the fiat portion of the paschen curve for a neon-argon gas mixture.

The row conductor plate .11 carries row conductor array 14 and border conditioning conductor (not shown) at the sides thereof. Column conductor plate 12 is similar to row conductor plate 11, and has column conductor array 16 in the writing or viewing area of the data display of the panel and border conditioning or side conductors (not shown). In a typical panel, the conductors may be spaced very closely together as, for example, on 20 mil centers and the conductors may be served with operating potentials from the same end or edge of the plates or from opposite ends in alternate fashion as disclosed in I-Ioehn US. Pat. No. 3,631,287.

Addressing circuits 20 for the row conductors and addressing circuits 22 for the column conductors may be of any suitable type such as multiplex resistor-diode selection matrices or individual addressing or pulsing circuits for each row or column conductor. An example of such matrix circuits is disclosed in the copending US. patent application Ser. No. 135,621, filed Apr. 19, 1971, by Donald Leuck and assigned to the same assignee as the instant patent application. Such matrix circuits float upon their respective sustainer sources 32 and 33, respectively. It will be noted that the sustainer generators 32 and 33 have a common point of reference potential SG. The row addressing circuits and the column addressing circuits are controlled by signals from data source and control circuit 40 which also controls the sustainer generators 32 and 33.

In accordance with this invention, it has been discovered that the effects of panel non-uniformity are minimized by applying all panel operating potentials at a magnitude such that every panel cell discharge occurs in the saturation mode.

For the purposes of this invention, the saturation mode of operation is defined inFIG. l by the section of the V versus A V characteristic to the right of point b; that is, the section B of the curve in which the cell voltage is essentially neutralized by the produced discharge or where V, is approximately equal to AV,,..

As mentioned above, studies shown that in normal operation any discharge site of panel 10, when supplied with a normal sustaining potential, will, in the ON" state, operate in a saturation mode; that is, the applied sustainer voltage signal pulse is essentially neutralized by the discharge as shown by point a in FIG. 1.. FIG. 1 is a plot of the change in wall voltage AV against the voltage appearing at the site, V,.. It will be noted that in the normal conditions the sustaining voltage V, when added to the wall voltage V results in the voltage V which is the normal saturation mode operating point for the site in this sustained operation. That is, the applied signal V (in saturation mode) is in essence completely neutralized by the wall voltage, e.g., the discharge. However, in the past, on addressing both the write and erase functions have been accomplished by attempting to set the wall voltage level at some more or less precise value by firing the sites in the portion or region of the curve marked A in FIG. 1.

The ideal is shown in FIG. 2 and the waveforms therefor shown in FIG. 4. As stated, deviations are allowed due to the stable nature of the discharge sequence, and, in fact, these deviations are inevitable due to panel non-uniformity. Thus, the characteristic curve of a panel operation shown in FIG. 5 hereof gives a more accurate representation of the panel characteristics. Note that the average write voltage (V,,) actually produces a variety of wall voltages with deviation 5 depending upon the particular sites selected. In accordance with the present invention, all sites are operated by applying selected write and/or erase voltages in the saturation mode (that is in the region B of FIG. 4) so that the panel non-uniformities become substantially irrelevant and have no effect on panel behavior. This is because all sites will reach the same potential when fired. Thus, the V must be at least equal to or greater than the saturation voltage V for the sustaining signal discharges plus the discharges associated with at least one member selected from a discharge initiating pulse (write) and/or discharge terminating pulse (erase).

I claim:

1. In a process for operating a multiple discharge panel with a thin gaseous discharge medium and having coated charge storage electrode arrays with charges being stored on the coating constituting a wall voltage and wherein the saturation mode at each discharge site occurs when the voltage characteristic of the panel, V is approximately equal to the change of wall voltage, AV caused by charges stored on the coating at the respective sites, comprising the step of applying to all electrodes in the panel sustaining potential signals of a selected magnitude, and to selected electrodes thereof a discharge condition manipulating voltage pulse of a sufficient magnitude to cause every discharge initiated by said discharge condition manipulating voltage pulses to occur in the saturation mode and every discharge after the first due to said wall voltage occurring in said saturation mode.

2. The invention defined in claim 1 wherein said saturation mode is as defined in FIG. 1 by the section of the V versus AV characteristic to the right of point b.

3. The invention defined in claim 1 wherein said discharge condition manipulating voltage pulse is the discharge initiating pulse voltage.

4. The invention defined in claim 1 wherein said discharge condition manipulating voltage pulse is the discharge terminating pulse voltage. 

1. In a process for operating a multiple discharge panel with a thin gaseous discharge medium and having coated charge storage electrode arrays with charges being stored on the coating constituting a wall voltage and wherein the saturation mode at each discharge site occurs when the voltage characteristic of the panel, VC, is approximately equal to the change of wall voltage, Delta VW, caused by charges stored on the coating at the respective sites, comprising the step of applying to all electrodes in the panel sustaining potential signals of a selected magnitude, and to selected electrodes thereof a discharge condition manipulating voltage pulse of a sufficient magnitude to cause every discharge initiated by said discharge condition manipulating voltage pulses to occur in the saturation mode and every discharge after the first due to said wall voltage occurring in said saturation mode.
 2. The invention defined in claim 1 wherein said saturation mode is as defined in FIG. 1 by the section of the Vc versus Delta Vw characteristic to the right of point b.
 3. The invention defined in claim 1 wherein said discharge condition manipulating voltage pulse is the discharge initiating pulse voltage.
 4. The invention defined in claim 1 wherein said discharge condition manipulating voltage pulse is the discharge terminating pulse voltage. 